It is known that the condition of maximum efficiency of a system for distribution of electrical energy is achieved when the power generated and introduced into the corresponding distribution network is equivalent to the one effectively absorbed by the set of the electrical appliances connected to the mains, namely, when the total amount of electrical power generated is in equilibrium with the total amount of power absorbed. Situations of inefficiency emerge, instead, when there exists a imbalance between the power generated and the one effectively required by the totality of the appliances connected to a given network for distribution of electrical energy.
In the case where, in a given instant, the power demand is significantly lower than the power produced, it is necessary, in order to Prevent any waste, to reduce the production of electrical energy through, for example, the reduction of the power delivered or the de-activation of one or more generators. Instead, when at a given instant the power demand tends to exceed the power effectively introduced into a given distribution network, then it is necessary, in order to prevent the risk of collapse of the mains supply (black-out), to set in operation one or more supplementary generators or, if these are already active with reduced power, to increase the power delivered in order to guarantee a condition of substantial re-balance between the power produced and the power absorbed.
Since the operations for de-activation and, above all, the operations for activation of supplementary generators of electrical energy produce inefficiencies and result on an annual basis, with reference, for example, to a country such as Great Britain or Italy, in an increase in the management costs of tens of millions of pounds or euros and in an increase of millions of tons of CO2 introduced into the atmosphere, it is very important to seek to promote development of techniques designed to minimize the sudden fluctuations of total absorption of electrical power by the ensemble of the appliances connected to a given network for distribution of electrical energy.
An interesting technique for minimizing sudden fluctuations of absorption of electrical power is described in U.S. Pat. No. 4,317,049 and is based upon the concept of “Dynamic Demand Control” (DDC), i.e., upon the dynamic control of the power demand performed directly and automatically by the appliances themselves. According to said technique, a set of electrical appliances, connected to a given distribution network, can modify the corresponding power consumption, within given limits and without jeopardizing their own functionality, in order to minimize sudden variations of the total absorption of electrical power by said distribution network, in accordance with the effective conditions of load of the latter, detected through the measurement of the corresponding mains frequency. It is known, in fact, that the value of the mains frequency constitutes a reliable indicator of the condition of load of a given network for distribution of electrical energy. In particular, when the consumption of the totality of the appliances tends to exceed the amount of electrical power that can be supplied by the mains, the frequency tends to drop with respect to its nominal value (typically equal to 50 or 60 Hz) by a few hundredths of Hertz, according to a known law; and, instead, when the power consumption is lower than the mains potential, the frequency tends to increase in a similar way with respect to its nominal value. The aforesaid solution envisages, hence, appropriate reduction of the power absorptions of the individual electrical appliances when the mains frequency decreases by a given quantity with respect to its nominal value, and appropriate increase of said absorptions when the mains frequency tends to exceed its own nominal value.
The fact that the totality of a significant set of electrical appliances is able to monitor, instant by instant, the possible variations of the mains frequency with respect to its nominal value and is able to react in the same instant to said variations, guarantees that said operations of reduction or increase of power absorption will occur in a perfectly synchronous way and hence such as to produce, by superposition of the effects, the desired corrective action.
The technique described in U.S. Pat. No. 4,317,049 moreover envisages that the control system of each electrical appliance is able to vary the power absorption associated to the corresponding internal electrical loads, without jeopardizing proper functionality of the appliance, i.e., without penalizing the quality of the performance offered to the user.
The electrical appliances most suited to perform the DDC function are the ones that are able to delay or anticipate their own absorption of electrical power without jeopardizing their own functionality for the benefit of the user. Possible non-exhaustive examples of said electrical appliances are air-conditioning systems, boilers, and household cooling appliances (refrigerators and freezers). The cooling appliances, in particular, represent the most interesting products, by virtue of their extremely wide diffusion. Other examples can be represented by electrical household appliances of discontinuous use (such as washing machines, dish-washers, and dryers, distinguished by phases of heating with high current absorption) that are able to delay according to the need, in relation to the state of overloading of the electrical mains, the step of heating of water or air, increasing the duration of the operating cycle but guaranteeing the same quality of the final performance.
The practical application of the aforesaid technique, regarding the minimization of possible sudden fluctuations of the total power absorption of a given network for distribution of electrical energy, presupposes the connection to said network of a sufficiently high number of electrical appliances capable of self-regulating their own consumption on the basis of the value of the mains frequency. In actual fact, however, there currently exist problems that prevent diffusion on a large scale of electrical appliances, in particular electrical household appliances, that are provided by this important feature, so that the applicability of the DDC function still proves rather remote. The main problems that constitute an obstacle to diffusion of electrical appliances, in particular electrical household appliances, capable of self-regulating their own consumption in accordance with the value of the mains frequency, are substantially the following two:
1. non-negligible cost of the DDC function (estimated at around 2-3 euros), which can be supported only by high-range products, the volumes of which are, however, insufficient for ensuring an effective action of compensation (proper, precisely, to the DDC function) in regard to sudden variations of the total power absorbed by the set of all the appliances connected to a given network for distribution of electrical energy;
2. current lack of incentives by national governments and/or by companies producing and distributing electrical energy, aimed at redistributing, given the marked economic and environmental benefit deriving from an efficient system of dynamic demand, part of said benefits in favour of manufacturers of electrical appliances provided with the DDC function and the corresponding purchasers and users.
It is evident that, a solution of the latter problem creates premises that are important for favouring the solution to the former problem.
In this connection, of considerable importance is the positive action currently performed by the British government, which, in order to stimulate the production and purchase of electrical household appliances (in particular refrigerators) that incorporate the DDC function, has recently promulgated a law that creates the conditions for the definition of appropriate instruments of incentivization in the use of “dynamic-demand technologies”. This is the so-called “HL Bill 106” of May 12, 2006, entitled “Climate Change and Sustainable Energy Bill”, which, amongst the various actions envisaged, also includes, through Art. 18, production, within twelve months from entry into force of the law itself, of a document that describes quantitatively the benefits, in terms of reduction of emissions of gases noxious for the environment, deriving from the use of DDC technologies.